外文翻譯---可編程控制器的介紹及未來發(fā)展

1、<p><b>　　英文資料翻譯</b></p><p>　　題目Programming controller introduction </p><p>　　院 系 中德機電學(xué)院 </p><p>　　專 業(yè) 電氣自動化技術(shù) </p><p>　　班 級

2、 0802 </p><p>　　學(xué)生姓名 </p><p>　　學(xué) 號 100081756 </p><p>　　指導(dǎo)教師 </p><p>　　2011 年 4 月</p><p>　　Programming

3、controller introduction </p><p>　　Motivation</p><p>　　Programmable Logic Controllers (PLC), a computing device invented by Richard E. Morley in 1968, have been widely used in industry including

4、manufacturing systems, transportation systems, chemical process facilities, and many others. At that time, the PLC replaced the hardwired logic with soft-wired logic or so-called relay ladder logic (RLL), a programming l

5、anguage visually resembling the hardwired logic, and reduced thereby the configuration time from 6 months down to 6 days [Moody and Morley, </p><p>　　Although PC based control has started to come into place,

6、 PLC based control will remain the technique to which the majority of industrial applications will adhere due to its higher performance, lower price, and superior reliability in harsh environments. Moreover, according to

7、 a study on the PLC market of Frost and Sullivan [1995], an increase of the annual sales volume to 15 million PLC per year with the hardware value of more than 8 billion US dollars has been predicted, though the prices o

8、f c</p><p>　　Though PLC are widely used in industrial practice, the programming of PLC based control systems is still very much relying on trial-and-error. Alike software engineering, PLC software design is

9、facing the software dilemma or crisis in a similar way. Morley himself emphasized this aspect most forcefully by indicating [Moody and Morley, 1999, p. 110]:</p><p>　　`If houses were built like software proj

10、ects, a single woodpecker could destroy civilization.”</p><p>　　Particularly, practical problems in PLC programming are to eliminate software bugs and to reduce the maintenance costs of old ladder logic prog

11、rams. Though the hardware costs of PLC are dropping continuously, reducing the scan time of the ladder logic is still an issue in industry so that low-cost PLC can be used.</p><p>　　In general, the productiv

12、ity in generating PLC is far behind compared to other domains, for instance, VLSI design, where efficient computer aided design tools are in practice. Existent software engineering methodologies are not necessarily appli

13、cable to the PLC based software design because PLC-programming requires a simultaneous consideration of hardware and software. The software design becomes, thereby, more and more the major cost driver. In many industrial

14、 design projects, more than SO0/a o</p><p>　　In addition, current PLC based control systems are not properly designed to support the growing demand for flexibility and manufacturing systems. A further proble

15、m, impelling the need for a systematic design methodology, is the increasing software complexity in large-scale projects.</p><p>　　1.2 Objective and Significance of the Thesis</p><p>　　The objec

16、tive of this thesis is to develop a systematic software design methodology for PLC operated automation systems. The design methodology involves high-level description based on state transition models that treat automatio

17、n control systems as discrete event systems, a stepwise design process, and set of design rules providing guidance and measurements to achieve a successful design. The tangible outcome of this research is to find a way t

18、o reduce the uncertainty in managing the control so</p><p>　　A systematic approach to designing PLC software can overcome deficiencies in the traditional way of programming manufacturing control systems, and

19、 can have wide ramifications in several industrial applications. Automation control systems are modeled by formal languages or, equivalently, by state machines. Formal representations provide a high-level description of

20、the behavior of the system to be controlled. State machines can be analytically evaluated as to whether or not they meet the desired g</p><p>　　Customer-Driven Manufacturing</p><p>　　In modern m

21、anufacturing, systems are characterized by product and process innovation, become customer-driven and thus have to respond quickly to changing system requirements. A major challenge is therefore to provide enabling techn

22、ologies that can economically reconfigure automation control systems in response to changing needs and new opportunities. Design and operational knowledge can be reused in real-time, therefore, giving a significant compe

23、titive edge in industrial practice.</p><p>　　Higher Degree of Design Automation and Software Quality</p><p>　　Studies have shown that programming methodologies in automation systems have not bee

24、n able to match rapid increase in use of computing resources. For instance, the programming of PLC still relies on a conventional programming style with ladder logic diagrams. As a result, the delays and resources in pro

25、gramming are a major stumbling stone for the progress of manufacturing industry. Testing and debugging may consume over 50% of the manpower allocated for the PLC program design. Standards [IEC 608</p><p>　　A

26、 systematic approach will increase the level of design automation through reusing existing software components, and will provide methods to make large-scale system design manageable. Likewise, it will improve software qu

27、ality and reliability and will be relevant to systems high security standards, especially those having hazardous impact on the environment such as airport control, and public railroads.</p><p>　　System Compl

28、exity</p><p>　　The software industry is regarded as a performance destructor and complexity generator. Steadily shrinking hardware prices spoils the need for software performance in terms of code optimizatio

29、n and efficiency. The result is that massive and less efficient software code on one hand outpaces the gains in hardware performance on the other hand. Secondly, software proliferates into complexity of unmanageable dime

30、nsions; software redesign and maintenance-essential in modern automation systems-becomes</p><p>　　Design Theory Development</p><p>　　Today, the primary focus of most design research is based on

31、mechanical or electrical products. One of the by-products of this proposed research is to enhance our fundamental understanding of design theory and methodology by extending it to the field of engineering systems design.

32、 A system design theory for large-scale and complex system is not yet fully developed. Particularly, the question of how to simplify a complicated or complex design task has not been tackled in a scientific way. Further&

33、lt;/p><p>　　Application in Logical Hardware Design</p><p>　　From a logical perspective, PLC software design is similar to the hardware design of integrated circuits. Modern VLSI designs are extreme

34、ly complex with several million parts and a product development time of 3 years [Whitney, 1996]. The design process is normally separated into a component design and a system design stage. At component design stage, sing

35、le functions are designed and verified. At system design stage, components are aggregated and the whole system behavior and functionality is te</p><p><b>　　PLC</b></p><p>　　PLC（progr

36、ammable logical controller）face ever more complex challenge these days. Where once they quietly relays and gave an occasional report to a corporate mainframe, they are now grounded into cells, give new jobs and new langu

37、ages, and are forced to compete against a growing array of control products. For this year’s annual PLC technology update, we queried PLC makers on these topics and more.</p><p>　　Programming languages</p

38、><p>　　Higher level PLC programming languages have been around for some time, but lately their popularity has been mushrooming. As Raymond Lavelle, vice president and general manager, Siemens Energy and Automat

39、ion. Inc, Programmable Controls Division, points out :”As programmable controls are being used for more and more sophisticated operations, languages other than ladder logic become more practical, efficient, and powerful.

40、 For example, it's very difficult to write a trigonometric function using lad</p><p>　　PLC in process control</p><p>　　Thus far, PLC have not been used extensively for continuous process con

41、trol. Will this continue? ”The feeling that I’ve gotten,” says Ken Jeannette, manager, product planning, Series One and Series Six products, at GE Frame North America, "is that PLC will be used in the process indust

42、ry but not necessarily for process control.”</p><p>　　Several vendors-obviously betting that the opposite will happen-have introduced PLC optimized for process applications. Rich Ryan, commercial marketing,

43、Allen-Bradley Programmable Controls Div, cites PLC increasing use in such industries as food, chemicals, and petroleum. Ryan feel there are two types of applications in which they’re appropriate.” ,he says, "is wher

44、e the size of the process control system that's being automated doesn’t justify DCS[distributed control systems].With the starting p</p><p>　　Bill Barkovtz, president of Triconex, predicts that "all

45、 future controllers that come out in the process control system business will embrace a lot more PLC technology and a lot more PLC functionality than they ever did before.”</p><p>　　Communications and MAP<

46、;/p><p>　　Communications are vital to an individual automation cell and to the automated factory as a whole. We've heard a lot about MAP in the last few years, and a lot of companies have jumped on the band

47、 wagon. Many, however were disappointed when a fully-defined and completed MAP specification didn’t appear immediately. Says Larry Kumara .Right now , MAP is still a moving target for the manufacturers specification that

48、 is not final. Presently, for example, people are introducing products to meet the M</p><p>　　Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example , has an ongoin

49、g MAP-compatibility program, but Frank Newborn, vice president of Omron’s Industrial Division, reports that because of the lack of a firm definition, Omron's PLC don't yet talk to MAP.</p><p>　　Since

50、 it’s unlikely that an individual PLC would talk to broadband MAP anyway, makers are concentrating n proprietary networks. According to Sal, users fear that if they do get on board and vendors withdraw from MAP, they wil

51、l pulse width modulation control system be the ones left holding a communications structure that’s not supported.</p><p>　　PLC Introduction</p><p>　　Programmable controller is the first in the l

52、ate 1960s in the United States, then called Plc programmable logic controller (Programmable Logic Controller) is used to replace relays. For the implementation of the logical judgment, timing, sequence number, and other

53、control functions. The concept is presented Plc General Motors Corporation. Plc and the basic design is the computer functional improvements, flexible, generic and other advantages and relay control system simple and eas

54、y to operate, s</p><p>　　In the mid-1970s, the Plc has been widely used as a central processing unit microprocessor, import export module and the external circuits are used, large-scale integrated circuits e

55、ven when the Plc is no longer the only logical (IC) judgment functions also have data processing, PID conditioning and data communications functions. International Electro technical Commission (IEC) standards promulgated

56、 programmable controller for programmable controller draft made the following definition : program</p><p>　　First, high reliability, anti-interference capability;</p><p>　　Second，programming vis

57、ual, simple;</p><p>　　Third, adaptability good;</p><p>　　Fourth, functional improvements, strong functional interface.</p><p>　　可編程控制器的介紹及未來發(fā)展</p><p><b>　　1.1動力&l

58、t;/b></p><p>　　1968年，Richard E. Morley創(chuàng)造出了新一代工業(yè)控制裝置可編程邏輯控制器(PLC),現(xiàn)在，PLC已經(jīng)被廣泛應(yīng)用于工業(yè)領(lǐng)域，包括機械制造也、運輸系統(tǒng)、化學(xué)過程設(shè)備、等許多其他領(lǐng)域。初期可編程控制器只是用一種類似于語言的軟件邏輯于代替繼電器硬件邏輯，并且使開發(fā)時間由6個月縮短到6天。</p><p>　　雖然計算機控制技術(shù)已經(jīng)產(chǎn)生，但是PL

59、C控制因為它的高性能、成本低、并且對惡劣的環(huán)境有很強的適應(yīng)能力而在工業(yè)控制的廣泛應(yīng)用中保持優(yōu)勢。而且，盡管硬件的價格在逐漸下跌，據(jù)估計，根據(jù)Frost和Sullivan對PLC市場的調(diào)查研究表明，每年銷售硬件的價格要比銷售PLC的價格（一千五百萬）至少多出八十億美元。PLC的創(chuàng)造者Richard E. Morley十分肯定的認(rèn)為目前PLC市場是一個價值五十億的工業(yè)</p><p>　　雖然PLC廣泛應(yīng)用于工業(yè)控制

60、中，PLC控制系統(tǒng)的程序依然和語法有關(guān)。和軟件過程一樣，PLC的軟件設(shè)計也以同樣的方式會遇到軟件錯誤或危機。Morley在演講中著重強調(diào)了這個方面。</p><p>　　如果房子建造的像軟件過程一樣，那么僅僅一只啄木鳥就可以摧毀文明。特別的，PLC程序要解決的實際問題是消除軟件錯誤和減少老式梯形邏輯語言的花費。盡管PLC的硬件成本在繼續(xù)下降，但是在工業(yè)控制上減少梯形邏輯的掃描時間仍然是一個問題，以至于可以用到低耗

61、時的PLC。</p><p>　　一般來說，和其他領(lǐng)域相比生產(chǎn)PLC的周期要短很多。例如，在實踐中，VISI設(shè)計是一種有效的計算機輔助設(shè)計。PLC不需要使用目前的以軟件設(shè)計為基礎(chǔ)軟件工程方法論，因為PLC程序要求對軟件和硬件搜都要考慮到。因此，軟件設(shè)計越來越成為花費動力。在許多的工業(yè)設(shè)計工程中，超過的人力分配給了控制系統(tǒng)設(shè)計和安裝，并且他們要對。PLC程序測試和排除錯誤，</p><p>

62、　　再者，PLC控制系統(tǒng)不適合設(shè)計對適應(yīng)性和重構(gòu)有越來越多要求的生產(chǎn)系統(tǒng)。一個更深入的問題是在大規(guī)模的工程中軟件越來越復(fù)雜，促使要有一個系統(tǒng)化的設(shè)計方法論。</p><p>　　1.2主題的客觀性和重要性</p><p>　　主題的客觀性是為PLC自動控制系統(tǒng)建立一個系統(tǒng)化的軟件設(shè)計方法論。這個設(shè)計方法論包括以狀態(tài)轉(zhuǎn)換模型為基礎(chǔ)的精確的描述，這個轉(zhuǎn)臺轉(zhuǎn)換模型是自動控制系統(tǒng)的抽象系統(tǒng)。方法論

63、還包括一個逐步的設(shè)計過程，并且要設(shè)置一個設(shè)計規(guī)則，這樣才能為一個成功的設(shè)計提供導(dǎo)向和方法。這項研究的真正目的是找到一個減少控制軟件發(fā)展過程的不穩(wěn)定性的方法，也就是說，減少程序和調(diào)試時間以及他們的變化，以增強自動控制系統(tǒng)的適應(yīng)性，并且通過調(diào)整軟件使得軟件可以再度使用。這樣的目的是為了克服目前程序策略的不足之處，而目前的程序策略是以個人軟件開發(fā)者的經(jīng)驗為基礎(chǔ)的。</p><p>　　一個系統(tǒng)化的設(shè)計PLC程序的方法可

64、以克服傳統(tǒng)程序生產(chǎn)控制系統(tǒng)的缺點，并且在一些工業(yè)應(yīng)用總有很大的不同。自動控制系統(tǒng)是狀態(tài)模型用公式語言或等價的語言描述的。公式描述對被控制的系統(tǒng)的行為提供一個精確的描述?？梢酝ㄟ^分析估計看狀態(tài)模型是否達到想要的目標(biāo)，第二，狀態(tài)模型的描述提供結(jié)構(gòu)描述，這個結(jié)構(gòu)描述可以說明邏輯要求和如細節(jié)安全規(guī)則的限制。第三，好的控制系統(tǒng)設(shè)計是對自動控制代碼生成有益的——一種能夠產(chǎn)生可執(zhí)行的控制軟件的能力，不同的邏輯控制器可以減少程序掃描時間和執(zhí)行那個時間。

65、特別的，這個主題與隨后的部分的是有關(guān)的。</p><p><b>　　訂制生產(chǎn)</b></p><p>　　在現(xiàn)代制造業(yè)中，系統(tǒng)是用過程和結(jié)果的革新來描述的，變得Customer-Driven，并且因此不得不改變系統(tǒng)性能以快速做出反應(yīng)。因此，一個大的挑戰(zhàn)是提供技術(shù)以限制自動控制系統(tǒng)對變化需要和新機會的反應(yīng)，所以，設(shè)計和操作知識可以實時的被再次利用，在工業(yè)實踐中提供了一

66、個重要的競爭面。</p><p>　　高水平的自動化設(shè)計和軟件質(zhì)量</p><p>　　研究表明，在自動化系統(tǒng)中，程序?qū)崿F(xiàn)的方法已經(jīng)與計算機資源應(yīng)用的急速增長不能匹配。例如，可編程邏輯控制器（ＰＬＣ）程序仍然依靠一種方便的有邏輯梯形圖的程序?qū)崿F(xiàn)模式。結(jié)果，程序上的延遲和資源成了生產(chǎn)工業(yè)過程的主要絆腳石。在可編程邏輯控制器程序設(shè)計過程中，測試和調(diào)試可能會占用超過百分之五十的人力。在發(fā)展和傳播

67、“ＳＴＡＴＥ－ＯＦ－ＴＨＥ－ＡＲＴ”已經(jīng)形成標(biāo)準(zhǔn)[IEC 60848, 1999; IEC-61131-3, 1993; IEC 61499, 1998; ISO 15745-1, 1999]，但是，基本上這些標(biāo)準(zhǔn)都不能參與有效的程序和系統(tǒng)設(shè)計方面知識的革新。</p><p>　　系統(tǒng)的方法通過使用原有的軟件模塊，有助于增加設(shè)計自動化的水平，同時也將提供一種可管理的大規(guī)模系統(tǒng)設(shè)計的方法。同樣的，它也將改善軟件的質(zhì)

68、量的可靠性，以及關(guān)系到系統(tǒng)的較高安全標(biāo)準(zhǔn)，尤其是這些對環(huán)境有危害影響的，比如：機場控制、公共鐵路運輸。</p><p><b>　　系統(tǒng)復(fù)雜性</b></p><p>　　軟件工業(yè)被認(rèn)為是系統(tǒng)性能的破壞者和系統(tǒng)復(fù)雜性的產(chǎn)生者。逐漸下降的硬件價格，破壞了對通過優(yōu)化程序獲得的軟件性能的需要。其結(jié)果是，一方面造成了大量而低效率的程序代碼，另一方面并沒有獲得高的硬件性能。其次

69、，軟件變得難以掌握其程度的復(fù)雜；在現(xiàn)代自動化系統(tǒng)中，軟件設(shè)計和保持系統(tǒng)本質(zhì)幾乎變得不可能。尤其是，可編程邏輯控制器（ＰＬＣ）程序設(shè)計從二十五年前的兩條主線，發(fā)展到現(xiàn)在的成千上萬條?，F(xiàn)在安全性增加了，例如，關(guān)于防火的新措施，以及現(xiàn)代自動化系統(tǒng)的柔韌性增加了程序設(shè)計過程的復(fù)雜性。因此，軟件的使用周期花費是總共花費的一個固定不變的增長部分。百分之八十到九十的花費用于軟件維護、調(diào)試、優(yōu)化（改進）、和擴展以滿足不斷變換的需求。</p>

70、<p><b>　　設(shè)計理論發(fā)展</b></p><p>　　目前，大部分設(shè)計研究的主要焦點都集中在機械和電子產(chǎn)品上。這種有目的性的研究產(chǎn)生了一個副產(chǎn)品，就是通過推廣這中研究到系統(tǒng)工程設(shè)計領(lǐng)域，從而加固了我們對設(shè)計理論和技巧的基本理解。針對大規(guī)模和復(fù)雜系統(tǒng)的系統(tǒng)設(shè)計理論并沒有成熟。尤其是，對如何簡化一個繁冗而復(fù)雜的設(shè)計任務(wù)這一問題，仍然沒有被科學(xué)的處理。而且，正在設(shè)計理論和代表

71、計算機科學(xué)及運籌學(xué)研究的認(rèn)識論結(jié)果之間構(gòu)建一條橋梁，這樣的具體應(yīng)該是邏輯硬件電路設(shè)計。</p><p>　　在邏輯硬件設(shè)計方面的應(yīng)用</p><p>　　從邏輯學(xué)的角度來看，可編程邏輯控制器（PLC）的軟件設(shè)計類似與集成電路的硬件設(shè)計。現(xiàn)代超大規(guī)模集成電路設(shè)計（Very Large Scale Integration--VLSI）是及其復(fù)雜的，一個集成電路一般有幾百萬個晶體管，而且產(chǎn)品開發(fā)

72、周期大都三年左右。設(shè)計過程一般都分成局部功能塊設(shè)計和系統(tǒng)設(shè)計兩個階段。在局部功能塊設(shè)計階段，單個功能將被設(shè)計出來，并予以驗證。在系統(tǒng)設(shè)計階段，所有功能塊都將被整合起來，整個系統(tǒng)行為特性和功能將會通過仿真形式加以測試。一般來說，所有部分都完全的驗證是不可能的。因此，統(tǒng)計學(xué)可以作為可編程邏輯控制器（PLC）設(shè)計的一個例子，并有可能影響邏輯硬件設(shè)計。</p><p>　　PLC(可編程邏輯控制器)現(xiàn)在面臨著甚至更加復(fù)雜

73、的難題。曾經(jīng)PLC取代繼電器并且丟對共同的計算機主機提供不時的信息?，F(xiàn)在，她被分解成單元模塊，并分給新的任務(wù)和應(yīng)用新的語言。而且被迫與越來越多的一系列控制產(chǎn)品相競爭。每年一度的最新PLC技術(shù)會上，我們調(diào)查PLC生產(chǎn)者關(guān)于以下這些問題。</p><p><b>　　編程語言</b></p><p>　　高級PLC編程語言已經(jīng)在有些方面很普及。但是最近高級編程語言已經(jīng)迅速

74、發(fā)展。西門子的總經(jīng)理兼生產(chǎn)部長指出：“可編程控制在被廣泛的應(yīng)用與于精密操作，除了梯形圖邏輯以外的編程語言變得更加使用、有效和強大。例如，用梯形圖邏輯寫一個三角函數(shù)公式是非常困難的。”被接收的語言包括Boolean,控制系統(tǒng)流程圖編制，和如公式編制語言Graphtec和與它類似的語言，并且還有增加的重要語言如C語言和BASIC語言。</p><p><b>　　過程控制中的PLC</b><

75、;/p><p>　　PLC還沒有廣泛的應(yīng)用于過程控制中。是否會一直這樣下去呢？美國南部Fancy的經(jīng)理Ken Jeannette說：“我覺得PLC將被用于過程控制但是對于過程控制又不是必須的?！?lt;/p><p>　　一些廠家已經(jīng)將PLC的優(yōu)化程序應(yīng)用于過程控制中，他們十分確定PLC不會廣泛用于過程控制這樣的事情是不會發(fā)生的。Rich Ryan經(jīng)理提到PLC在食品、化學(xué)和石油等工業(yè)領(lǐng)域越來越多的

76、應(yīng)用。他認(rèn)為PLC適合應(yīng)用于場合有兩種，他說：“第一，過程控制系統(tǒng)的型號不適合離散控制系統(tǒng)，剛開始這些產(chǎn)品的價格非常的高。而一個可編程控制器以它的體積小，價格低順理成章的被應(yīng)用。第二，你必須把電路和邏輯緊密的結(jié)合愛來。例如，一組基本的控制器，連續(xù)的過程變量緊密的互相聯(lián)系在一起，以至于用可編程控制器來完成一系列的邏輯勝過沒有離散控制器的系統(tǒng)?！?lt;/p><p>　　通信和生產(chǎn)自動化協(xié)議（MAP）</p>

77、<p>　　通信對于個人自動單元是很重要的。在過去的幾年里，我們聽到許多關(guān)于生產(chǎn)自動化協(xié)議的事情，并且許多公司已經(jīng)加入大有成功希望的事業(yè)。然而，當(dāng)一個完整的生產(chǎn)自動化協(xié)議說明書沒有及時出現(xiàn)時許多公司都很失望。Larry Kotare說:”現(xiàn)在，生產(chǎn)自動化協(xié)議仍然是生產(chǎn)中一個發(fā)展的對象，一個說明書并不是最終的結(jié)果。例如，雖然當(dāng)新的生產(chǎn)自動化協(xié)議MAP3.0版本使用之時以MAP2.1版本為基礎(chǔ)的產(chǎn)品將會被汰，但是現(xiàn)在人們?nèi)匀粚?/p>

78、產(chǎn)品用于MAP2.1版。”</p><p>　　由于這些原因，許多PLC廠家緊盯著MAP的最新結(jié)果。如歐姆龍公司正在進行一個有關(guān)MAP兼容性的項目。但是歐姆龍生產(chǎn)部門總經(jīng)理Frank Newborn說由于缺少一個固定的標(biāo)準(zhǔn)，歐姆龍的產(chǎn)品并不涉及到MAP。</p><p>　　由于工業(yè)PLC無論何時不可能廣泛的涉及到MAP，生產(chǎn)廠家正在考慮專用網(wǎng)絡(luò)。根據(jù)Sal說法，用戶擔(dān)心如果他們廣泛的應(yīng)用

79、生產(chǎn)廠家將會收回MAP，這樣將會留下一個不支持通信的交流框架。</p><p>　　PLC簡介可編程控制器是60年代末在美國首先出現(xiàn)的，當(dāng)時叫可編程邏輯控制器PLC（Programmable Logic Controller），目的是用來取代繼電器。以執(zhí)行邏輯判斷、計時、計數(shù)等順序控制功能。提出PLC概念的是美國通用汽車公司。PLC的基本設(shè)計思想是把計算機功能完善、靈活、通用等優(yōu)點和繼電器控制系統(tǒng)的簡單易懂、操

80、作方便、價格便宜等優(yōu)點結(jié)合起來，控制器的硬件是標(biāo)準(zhǔn)的、通用的。根據(jù)實際應(yīng)用對象，將控制內(nèi)容編成軟件寫入控制器的用戶程序存儲器內(nèi),使控制器和被控對象連接方便。    70年代中期以后，PLC已廣泛地使用微處理器作為中央處理器，輸入輸出模塊和外圍電路也都采用了中、大規(guī)模甚至超大規(guī)模的集成電路，這時的PLC已不再是僅有邏輯(Logic)判斷功能，還同時具有數(shù)據(jù)處理、PID調(diào)節(jié)和數(shù)據(jù)通信功能。國際電工委員會(IE